The present invention relates generally to substrate processing technologies. More particularly, embodiments of the invention relate to methods and apparatuses for processing substrates (e.g., silicon-based wafers or wafers based on other types of material) in a plasma processing chamber.
Generally speaking, the substrate may be processed in a series of steps in which substrate materials are selectively removed (etched) or deposited or otherwise processed. The processed substrate (or dies cut from the processed substrate) may then be employed to form a variety of electronic devices, such as display panels or integrated circuits for example. Substrate processing technologies in general are well-known and will not be further elaborated here for brevity's sake.
Plasma-enhanced processing is also well-known and has proven to be particularly suitable for forming the extremely small and/or fine features required in modern electronic devices. Plasma etching, for example, employs plasma formed from a process gas (which may be a single gas or a mixture of different gases) to selectively etch material from exposed (e.g., unmasked) areas of the substrate. Various plasma generation technologies have been employed to form the plasma, including for example capacitively coupled plasma generation, inductively coupled plasma generation, ECR (electron-cyclotron resonance), microwave, and/or hybrids thereof.
In a typical capacitively coupled plasma (CCP) processing chamber, for example, two or more electrodes are disposed in a spatially separated manner, with at least one of the electrodes powered by one or more RF generator(s). In an example configuration, two electrodes are employed, with the chuck (substrate support) powered by an RF power supply via an RF match. The other electrode may, for example, be grounded and may be disposed above and in a spaced-apart relationship with the substrate (with the substrate disposed on the aforementioned chuck). In an example configuration, the space between the two electrodes may be further confined by a set of confinement rings in order to define a plasma generation region. Process gas is injected into this plasma generation region to be ignited into a plasma to process the substrate.
To facilitate discussion, FIG. 1 shows a highly simplified drawing of an example capacitively coupled plasma (CCP) processing chamber 102 having a powered lower electrode/chuck 104 and an RF supply 120. A substrate 106 is shown disposed on lower electrode/chuck 104 during substrate processing. An upper electrode 108 is shown disposed above and in a spaced-apart manner from substrate 106, conceptually forming a plasma generation region 110 in which plasma 112 may be formed from injected process gas (not shown to simplify the drawing).
Optional confinement rings 114 may be provided to confine plasma 112 in plasma generation region 110 as well as to control the pressure within plasma generation region 110. The CCP chamber 102 of FIG. 1 is highly simplified, as mentioned, and variations exist with respect to, for example, the type of chuck employed, the manner with which the process gas is injected, the manner with which pressure is controlled, the number of electrodes, the location of the electrodes, the number and frequencies of the RF power supplies, etc. Irrespective, capacitively coupled plasma processing chambers and their variations are well known.
Generally speaking, a larger substrate yields a larger number of cut dies. To increase production output (e.g., a greater number of electronic devices manufactured per unit of time), manufacturers strive to employ large substrates whenever possible. As the substrate increases in size, it becomes more challenging to maintain an acceptable level of process result uniformity (e.g., etch rate and/or etch depth). For larger substrates (e.g., 300 mm or above) processed in capacitively coupled plasma process chambers, maintaining a satisfactory level of radial uniformity (e.g., from the center of the substrate to the edge of the substrate) has proven to be challenging.
In view of the foregoing, improved methods and apparatus for processing substrates with improved process uniformity in a plasma processing system are desired.